This invention relates to binoculars.
In the final stages of manufacturing, the optical system of a new binocular must be placed in alignment so that the image will be undistorted when viewed through the eye pieces.
Several alignment procedures have been used in the manufacture of Japanese binoculars:
I. The so-called "orthodox" method comprises the use of a leaf or foil underneath the prism and using the eccentric ring of the objective to effect the adjustment.
II. Next to the "orthodox" method, the most stable system involves mounting the prism seat on its three mutually spaced pads within the prism chamber by means of three pairs of screws, each pair comprising a set screw and an adjusting screw. Use of this arrangement has been known to distort the prism seat some times causing prism chipping.
III. As an alternative to the foregoing, the edges of the prism seat are mounted on the pads by means of single screws with coil springs placed between the bottom surface of the seat and the top surface of the pad. Tightening or loosening of the screws causes adjustment of the seat and correspondingly of the prisms. This arrangement is fairly easy to use but not nearly so stable as the above.
IV. In a fourth system, a prism is tiltably held in its seat, the latter being immovably fastened to the interior wall of the chamber. An adjusting screw pierces the chamber wall and bears against the side of the prism. Turning the screw in or out controls the tilt of the prism for alignment purposes. Since the wall is thin it is difficult to prevent air leakage around the adjusting screw and the integrity of the seal of the chamber is jeopardized. Furthermore, the system inherently lacks stability, although it is the only one permitting adjustment of the alignment after the device has been assembled.
Objects of the present invention include providing a structural configuration that allows stable prism alignment without endangering the seal of the enclosed body cavity; that reduces the danger of introducing tension to the prism seat with the possibility of chipping the prism; that provides for stable alignment; and that can be finely adjusted even by a relatively unskilled worker.